1. Field of the Invention
The present invention relates to a method for constructing and cladding storage tanks and silos.
More specifically the invention is intended for cladding storage tanks and silos with enamelled steel, and this on the inside and outside.
2. Description of the Related Art
Such storage tanks are useful in industrial applications such as in the food industry, agriculture, mining, chemicals and petrochemicals, biological fuels, waste processing, water purification, desalination and similar.
It is known that enamelled steel can be used for the construction of storage tanks, whereby both the inside and outside of the tank present an enamelled surface. The enamelled steel on the outside of the tank does not need to be painted, and on the inside of a tank it provides an inert surface resistant to almost all conceivable materials that are stored therein.
Traditionally such storage tanks are constructed from prefabricated enamelled curved thick-walled steel segments that are fastened together in situ either by screwing them together with bolts, or by welding them together, either on site or in a construction facility.
Traditionally the method by which two double-sided enamelled curved thick-walled steel segments are riveted together is by a double row of bolts with nuts that all go through the two segments to be fastened together and hold them together.
A disadvantage of this conventional method is that all segments consist of pre-enamelled thick-walled steel, which makes these segments more expensive than non-enamelled metal segments.
Another disadvantage of this conventional method is that an unevenness or seam is created on the inside and outside of the storage tank, at the level of the joint of a pair of segments, which detrimentally affects the smoothness of the inside cladding and exposes the edge of the enamelled steel to the materials stored in the tank.
For segments that are fastened together with bolts, the section that is screwed together presents a potentially weaker resistance to the pressure and weight of the stored materials, which limits the height and diameter of the storage tank.
Another disadvantage of this conventional method to construct enamelled storage tanks is that the segments must be enamelled beforehand and frequently on both sides, which is an expensive batch process on account of the dimensions and weight of these segments.
Furthermore the use of enamelled hot-rolled thick steel is less suitable than enamelled cold-rolled thin steel with regard to open pores and fish scales, which is important for the quality of both the internal and external cladding of silos and tanks.